1. Field of the Invention
The present invention relates generally to vacuum chucks, and more specifically, to a vacuum chuck apparatus which is applicable for wet processing in semiconductor manufacturing.
2. Description of the Related Art
In semiconductor manufacturing processes, there are many occasions when semiconductor substrates or wafers must be handled to load, reload or unload them to or from a carrier or holder. In such cases, tweezers or forceps are widely used for handling. However, in order to avoid flaws or other damage caused by tweezers, vacuum chucks or Bernoulli flow chucks are increasingly being used.
Semiconductor processing includes many treatments which use water or chemicals. Such a process is called a wet process, as opposed to a dry process in which the wafer is treated in air or gaseous ambient. Many of these wet processes are carried out by using batch processing to increase their output. Several wafers are loaded in a holder, and immersed into chemicals to process them. In such batch processing systems, especially in wet processing, stains are sometimes left where the wafer contacts the holder, thus spoiling the uniformity of processing. Therefore, a problem of how to prevent such stain persists in the wet processing art.
From the view point of uniformity of products, however, a one by one processing system is better than a batch system. This is because each of the wafers can be checked, and the holding or contact points of the wafer can be shifted to prevent staining. Sometimes the wafer is held by its back surface to protect the front surface from effects caused by contact with a tool. In such cases, the wafer chuck becomes very important. For a dry process, vacuum chucks or the Bernoulli flow chucks can be used, but heretofore there have been no vacuum chucks which could be used in a wet process.